Important steps forward have been made in controlling viral burden and prolonging survival in HIV-1 infected individuals using highly active antiretroviral therapy (HAART). However, some HIV-1 infected humans and SIV infected macaques maintain a high virus burden despite treatment. The SIV/macaque model will be instrumental, therefore, in determining the mechanisms responsible for this dichotomy. Insight into the mechanisms that control responsiveness to treatment will in turn be critical to the development of strategies, such as the therapeutic, particle-mediated DNA vaccine against SIV being studied here, that not only enhance treatment of those responsive to antiretroviral therapy, but more importantly allow nonresponsive individuals to ultimately respond. In this project we will address the hypothesis that the immunologic component of nonresponsiveness to HAART, is the result of inappropriate interactions between the potent antigen presenting dendritic cells (DC) and CD4+ T-lymphocytes. Under this hypothesis, the outcomes of these DC/T-lymphocyte interactions are skewed and inappropriate and therefore do not effectively contribute to long-term control of viral replication. To provide mechanistic insight into responsiveness to HAART therapy, and the effects of the genetic adjuvant, E. coli heat-labile enterotoxin (LT), we will use DNA microarray technologies to identify genes differentially expressed by responders and nonresponders in multiple lymphoid tissues, and in dendritic cells (DC) therein. Our aims are to: (1) Identify genes that are differentially expressed in lymph nodes (LN) from responder and nonresponder rhesus macaques during health, acute infection, chronic infection, HAART, and therapeutic DNA vaccination; (2) Determine the properties of DC, T-lymphocytes, and natural killer (NK) cells in multiple anatomic compartments during the infectious and therapeutic courses in responder and nonresponder animals; (3) Measure the ability of a second generation genetic adjuvant to facilitate induction of appropriate SIV-specific immune responses in responder and nonresponder animals. The collaborative work contributed by this Project, in concert with Projects 1 and 2, will complement the resources and expertise of PowderJect Vaccines, and allow for a comprehensive investigation into the mechanisms controlling the success or failure of adjuvanted and non-adjuvanted therapeutic DNA vaccines in the SIV system.